1. Field of the Invention
The present invention relates to a shielded cable joining structure and to a method for joining a shielded cable.
2. Description of the Related Art
A termination structure for the above-noted type of shielded cable is disclosed in the Japanese Patent Application Laid-Open Publication No. 7-201383, in which a shielded cable is formed by an inner core wire that is made of a conductor, an inner insulation covering that covers the inner core wire, a braid that is provided around the periphery of the inner insulation covering, and an outer insulation covering that covers the braid.
In the above-noted related art, part of the outer insulation covering at the end part of the shielded cable is removed, the inner insulation covering and braid are separated from one another, and the ends of the inner core wire that is exposed at the end part of the inner insulation covering and the braid are each connected by means of a terminal fixture. Before crimping the terminal fixture onto the end of the braid, the end part of the braid is bundled together by heat-shrink tubing that contracts by the application of heat.
In the above-noted termination structure for a shielded cable, however, because the terminal fixture is crimped onto the end of the braid after the braid is separated from the inner insulation covering, not only is there a danger of damaging the braid when performing the crimping operation, but also there is a part thereof that is not shielded. Additionally, because it is essential to have a bundling member such as heat-shrink tubing in order to bundle together the end part of the braid, the task of termination was cumbersome.
Accordingly, it is an object of the present invention to improve on the above-noted drawbacks in the related art, by providing a shielded cable joining structure and joining method, whereby it is easy to achieve a reliable joining of a shield terminal to the exposed part of the braid, without damaging the braid.
In order to achieve the above-noted object, the present invention adopts the following basic technical constitution.
Specifically, from the first aspect of the present invention, there is provided a joining structure for a shielded cable, comprising an inner core wire made of a conductor, an inner insulation covering that covers the inner core wire, a braid that is provided around the outside periphery of the inner insulation covering, an outer insulation covering that covers the braid, and a shield terminal that has a crimping part that is crimped over the outer insulation covering, wherein the crimping part of the shield terminal and the braid are welded by melting away part of the outer insulation covering by resistive welding, in a condition in which the crimping part of the shield terminal is crimped.
In this shielded cable joining structure, by using resistive welding to melt away part of the outer insulation covering using resistive welding with the crimping part of the shield terminal crimped, so as to enable the achievement of a welding of the shield terminal crimping part and the braid, it is possible not only to minimize damage to the braid and broken connections, but also to improve the reliability of the connection. Additionally, because there is no need to separate the braid from the inner insulation or remove part of the outer insulation covering, the shielding performance is improved.
Preferably, the crimping part of the shield terminal may be substantially U-shaped, with mutually opposing end parts capable of making mutual contact at an inclination.
In this configuration, because the end parts of the substantially U-shaped crimping part that holds the braid of the shielded cable make contact with each other with no space therebetween, damage to and broken connections in slender braid wires are reliably prevented.
Preferably, the crimping part of the shield terminal may be substantially U-shaped, with mutually opposing end parts capable of making mutual contact along a direction that is parallel to the longitudinal direction of the braid.
In this joining structure, the U-shaped opposing crimping part enables easy and reliable connection to any grounding position, whether at a cable end or at an intermediate position therealong.
From the second aspect of the present invention, there is provided a method for joining a shield terminal to a prescribed position on a shielded cable which is formed by an inner core wire made of a conductor, an inner insulation covering that covers the inner core wire, a braid that is provided around the outside periphery of the inner insulation covering, and an outer insulation covering that covers the braid, the method having steps of setting a crimping part of the shield terminal over the outer insulation covering at a grounding position of the shielded cable, causing a pre-heating to flow between a pair of electrode tips while pressure is applied between the electrode tips so as to crimp the crimping part, thereby softening the outer insulation covering and removing it by means of the applied force, and causing a welding current to flow between the pair of electrode tips, so as to achieve a weld between the crimping part of the shield terminal and the braid.
In the above-described method of joining a shielded cable, by setting the crimping part of the shield terminal over outer insulation covering at a grounding point of the shielded cable, and then using a pre-heating current to melt away part of the outer insulation covering while crimping the crimping part, so as to achieve a weld between the crimping part and the part of the braid that is exposed by partial removal of the outer insulation covering, the need to separately remove part of the outer insulation covering is eliminated, thereby enabling a simplification of the process and improvement in workability.